This invention relates generally to semiconductor devices and in particular to field effect transistors having a conducting channel which is more heavily doped between a gate and a source region than between the gate and a drain region of the field effect transistor and a method for making the novel field effect transistor.
Presently gallium arsenide field effect transistors have a uniform, active conducting channel between the drain and source regions. For many applications it is desirable to have field effect transistors which have the characteristics of high output breakdown voltage with high output power and high gain for given frequency such as 18 gigahertz. It is known in the art that to achieve high power output in bipolar transistors a lightly doped i-layer is constructed between the base region and collector region of the transistor. This causes the collector to base capacitance to be low and thus leads to considerably higher cut-off frequencies. Furthermore, the lightly doped layer between the gate and drain results in high gate to drain as well as source to drain voltage breakdown which lead to higher power capability. Because the field effect transistor has a different structure than the bipolar transistor, an economical method of manufacturing a field effect transistor utilizing the i-layer does not exist in the prior art. The present invention provides a solution to this problem in the prior art and provides a novel field effect transistor and a method of making it.